The invention relates in general to diving equipment and in particular to a new and useful diver's rescue apparatus with a fillably buoyancy element and a breathing bag into which a respiratory gas mixture is metered from a compressed gas supply.
Such rescue apparatus is employed in particular for rapid ascent from damaged underwater craft whereby e.g. submarine crew members can come up from deep water. A buoyancy element provides the necessary buoyancy, a respiratory gas source supplying the ascending person with respiratory gas of suitable composition.
A known submarine rescue apparatus is described in G. Haux, Tauchtechnik (Diving Technology, German),. Volume 1, page 32, Berlin, Heidelberg, New York 1969. There, a respiratory gas mixture of for example 50% oxygen and 50% nitrogen is stored in a mixed-gas bottle under a maximum pressure of 200 kp/cm.sup.2. The gas flows via a pressure reducer and a downstream throttle into the breathing cycle to which the wearer of the apparatus is connected via a mouthpiece. Exhalation takes place via a breathing bag, from which the exhaled air, purified via a CO.sub.2 absorption cartridge is returned into the respiration cycle. In the known rescue apparatus, a constant inflow of the respiratory gas mixture takes place as a function of the diving depth to about 40 m. At greater depths, the inflow decreases noticeably due to the further increase of the counterpressure, and it stops entirely at a depth of about 80 m.
To be able to use the known rescue apparatus at still greater depths, the backpressure adjustment at the pressure reducer must be increased, so that the counterpressure at the greater depths can be overcome However, the apparatus wearer would then receive, also at great depths, a respiratory gas mixture with a physiologically unfavorable high oxygen partial pressure.
A known diving equipment according to German patent 10 97 848 has at least two compressed gas tanks containing oxygen and inert gas in different mixture ratios, the tanks being connected to a respiration cycle, in which equipment, depending on the diving depth, the admission of the respiratory gas mixture is established or interrupted. With this known apparatus, a respiratory gas mixture of higher oxygen content for small diving depths can be switched to a mixture of lower oxygen content for greater depths, and vice versa. For this purpose two pressure reducers and switches controlled by the water pressure are needed, which are arranged between the individual gas lines from the compressed gas tanks and the following header or collecting line. This results in a complicated layout, additional apparatus weight to be carried, and increased trouble proneness of the equipment as a whole, as it may occur through the existing proportioning mixing system.